Risa Rutter

Numerical Flow Simulation and Validation of an Electrical Submersible Pump

Computational Fluid Dynamics (CFD) is used to investigate the hydraulic performance of a centrifugal pump within the electrical submersible pump (ESP) unit in single-phase flow. The geometry consists of a three-stage centrifugal pump with an impeller and a diffuser in each stage. The stage performance is influenced by the inlet and outlet conditions of the stage, and therefore, three stages were modeled. The simulations were run at 3,500 RPM for various flow rates within the operating range. The k-e turbulence model and the shear stress transport (SST) turbulence model were used to compare the capabilities of the model on performance predictions. Simulations were run in steady and unsteady flow conditions with a single vane and a full pitch model.Hydraulic performance such as efficiency, pump head, and break horse power (BHP) obtained from numerical analysis were compared with the test results to validate the CFD model. The comparison results revealed that the CFD overpredicts the pump head and underpredicts the BHP by 5 to 10%. The discrepancy between measurements and predictions are reasonable because the hydraulic leakage and bearing power losses are not modeled in CFD. The overall predicted efficiency is higher than the measurements because of overpredicted head and underpredicted BHP. Comparing numerical simulations with different turbulent models showed no significant difference between the k-e model and the SST model. The steady/ unsteady flow comparison also showed similarity in the hydraulic performance near the best efficiency point. For design purposes, steady flow simulation with a single vane and the k-e model were used to cut computational time.Copyright

Validation and Optimization of Heat Transfer in the Electrical Submersible Pump Motor by CFD

In oilfield applications, an electrical submersible pumping (ESP) system is placed inside the wellbore to provide the necessary energy to lift the fluids to the surface when the reservoir pressure is not sufficient. The ESP system consists of an electric motor, seal section, rotary gas separator (optional), multistage centrifugal pump, electric power cable, motor controller and transformers. The electric motor is placed on the bottom of the unit, and the production fluids are allowed to pass around the motor in order to cool it. The motor generates heat while operating. Study on the temperature rise inside the motor is important to prevent components from failing due to overheating. The temperature rise inside a motor has not been studied extensively. In this work, the temperature of components inside an electric motor was measured under different loading conditions, fluid viscosity and temperature. After testing, the computational fluid dynamic (CFD) was used to model the temperature heat rise in the same motor under the same conditions. The CFD models were validated by the test data within ± 5% error. Furthermore, the validated CFD model was used to calculate the heat rise for different insulation and bedding materials. These computational results from CFD are used to optimize the design of the electrical motor.Copyright